Our Environment — Science STD 10 — Question

1. What is an ecosystem? List its two main components.
2. We do not clean ponds or lakes, but an aquarium needs to be cleaned regularly. Explain.

How is Earth kept warm by nature? Describe in detail.

State the cause of dispersion of white light passing through a glass prism. How did Newton show that white light of sun contains seven colours using two identical glass prisms. Draw a ray diagram to show the path of light when two identical glass prisms are arranged together in inverted position with respect to each other and a narrow beam of white light is allowed to fall obliquely on one of the focus of the first prism.

Determine how far an object must be placed in front of a converging lens of focal length 10cm in order to produce an erect (upright) image of linear magnification 4.

Compare and contrast biomass and hydroelectricity as sources of energy.

Taking the example of an element of atomic number 16, explain how the electronic configuration of the atom of an element relates to its position in the modern periodic table and how valency of an element is calculated on the basis of its atomic number.

What is a magnetic field? How can the direction of magnetic field lines at a place be determined?

A sulphate salt of Group 2 element of the Periodic Table is a white, soft substance, which can be moulded into different shapes by making its dough. When this compound is left in open for some time, it becomes a solid mass and cannot be used for moulding purposes. Identify the sulphate salt and why does it show such a behaviour? Give the reaction involved.

What are outside raw materials used for by an organism?

Why does the rate of breathing in aquatic animals is faster than others?